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Combined QT prolonging medicines — GPhC CRA MCQ

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HardDrug InteractionsCombined QT prolonging medicinesGPhC CRA

A 74-year-old woman takes sotalol for atrial fibrillation and is prescribed clarithromycin for a chest infection. She has a history of low potassium with diuretics. What is the most important interaction to flag?

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Correct answer: A — Clarithromycin with sotalol may increase QT prolongation and arrhythmia risk

Both sotalol and clarithromycin can prolong the QT interval, increasing risk of serious arrhythmia. Hypokalaemia is an additional risk factor. The prescriber should be contacted for an alternative antibiotic or monitoring plan. The other options do not reflect the main safety concern.

Reference: BNF; MHRA